Method for producing composite insulator

Abstract

A method of producing a composite insulator having a sheath and shed portions molded around a core rod, grasping metal fittings engagingly fitted and fixed at both end portions of the core rod, the sheath covering the core rod between the grasping metal fittings on the whole circumference of the core rod, and a plurality of shed portions extruding radially outwardly from the sheath at plural positions spaced from each other in the longitudinal direction of the core rod, by filling an insulative high molecular material and subsequent vulcanization thereof in the cavity of molding die portions. The methods includes positioning and retaining the core rod at a desired position in the cavity of the molding die portions by means of retaining rings engagingly fitted on the grasping metal fittings and allowing an excess portion of the insulative high molecular material filled in the cavity to flow out to the exterior of the cavity between the grasping metal fittings and the retaining rings.

What is claimed is: 
     
       1. A retaining ring for positioning and retaining a core rod in molding die portions at a desired position in the cavity of the molding die portions, while circumscribing the grasping metal fittings engagingly fitted and fixed on the both end portions of the core rod, comprising supporting portions on the inner circumferential surface of the retaining ring, which supporting portions contacting with the outer circumferential surfaces of the grasping metal fittings, and gaps defined along the length of the axial direction of the retaining rings between the inner circumferential surfaces of the retaining rings and the outer circumferential surfaces of the grasping metal fittings. 
     
     
       2. The retaining ring of claim 1, comprising supporting portions and outlet portions respectively provided at plural portions on the circumference of the retaining ring. 
     
     
       3. The retaining of claim 1, comprising the supporting portions comprised of a fluorine series resin.